Multidisciplinary Investigation of the Evolution of Persistently Active Basaltic Volcanoes by Jeffrey Mark Zurek M.Sc., Simon Fraser University 2010 B.Sc., University of Victoria, 2007 Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Department of Earth Sciences Faculty of Science Jeffrey Mark Zurek 2016 SIMON FRASER UNIVERSITY Summer 2016 Approval Name: Jeffrey Mark Zurek Degree: Doctor of Philosophy Title: Multidisciplinary Investigation of the Evolution of Persistently Active Basaltic Volcanoes t Examining Committee: Chair: John Clague Professor Glyn Williams-Jones Senior Supervisor Associate Professor Séverine Moune Supervisor Physicien-Adjoint Laboratoire Magmas et Volcans Observatoire de Physique du Globe de Clermont-Ferrand Dan Gibson Supervisor Associate Professor Nathan Hayward Internal Examiner Adjunct Faculty Joachim Gottsmann External Examiner Associate Professor School of Earth Sciences University of Bristol Date Defended/Approved: April 7, 2016 ii Abstract The size, shape, location and/or chemical evolution of basaltic magma plumbing systems at most volcanoes is not well constrained. Having this information beneath active systems allows scientists to target areas which will likely be the first to display volcanic unrest. With these constraints and datasets that cover long periods of time or include anomalous topographic features, we can start to investigate how a volcanic system has changed over time. To accomplish this, geochemical and geophysical studies at Masaya volcano (Nicaragua) and Mauna Loa volcano (Hawaii, USA) were conducted. Melt Inclusions were collected from Masaya volcano to investigate the processes within the magma chamber. The almost unchanging chemistry of the whole rock, crystals and melt inclusions regardless of which eruptive cone sampled suggests that the system is buffered in both temperature and chemistry. A large deep reservoir with rapid transit times to the surface could explain the data. Bouguer gravity mapping data at Masaya and Mauna Loa volcanoes were collected, processed and inverted to constrain the location and volumes of density anomalies at depth. Beneath Masaya volcano, the gravity data provides evidence of a very large intrusive complex (< 900 km3) at 4-9 km depth as well as several small shallow anomalies perhaps due to ring dykes around a buried caldera rim. This study strengthens arguments that Masaya does not have a large shallow magmatic system and that shallow endogenous growth is minimal. Gravity mapping and inversions from Mauna Loa provide evidence for relatively rapid rift zone migration most likely caused by a large edifice destabilizing event. The massive Ālika debris flows are contemporaneous with the age of rift zone migration suggesting that mass wasting is the cause. Keywords: Volcanology; Geochemistry, Geophysics; Magnetics; Gravity; Melt inclusions iii Acknowledgements There are too many people to acknowledge but I will try to mention everyone. First to Anna and my family, the support and understanding has made finishing possible even with the arrival of Gregory my second son. Glyn thank you for your guidance and empathy through this second degree; in which I have been able to choose what projects to take on, allowing for complete academic freedom. Séverine thank you for agreeing to be a part of my committee, there is no way I would have been able to pull Chapter 3 off without you. Due to you, I, a geophysicist, now know enough to be dangerous with geochemistry; no small feat. Dan, whenever I needed anything you were there to provide insightful advice or give something a quick proof read. The instrument development project got as far as it did largely thanks to the university’s crack crew at the SFU electronics shop and the metal/wood shop. They fabricated parts, built the data logger interfaces and provided a sounding board to test ideas. Without that data logger Chapter 4 would have significantly less magnetic data. Whenever I needed to bounce ideas around or needed some kind of code or software help, my lab mates and friends were there to save the day. Nathalie you were always available to answer my chemistry questions and point me towards possible solutions. Patricia, besides partaking in the banter, crafting of field songs and plain silliness, having a different perspective around helped my own research looking at survey design in a more quantitative way. Craig without you I swear it would have taken me an extra two months to finish this document, it was as if you knew what thing I was going to be doing next and forged ahead producing easy to use scripts. To my missing in action co-author, Nicaragua companion and previous OU PhD student, Guillermo, this document sums up a lot of the discussions and brainstorms we had while collecting this data. I hope it does it justice. I would be remiss if I forgot to thank the department’s staff for keeping me on track and mostly out of trouble. Special shout out to Glenda for looking after the bureaucratic papers I always seemed to mess up and Matt and Rodney for always being there to trouble shoot a problem. iv Table of Contents Approval .............................................................................................................................ii Abstract ............................................................................................................................. iii Acknowledgements ...........................................................................................................iv Table of Contents .............................................................................................................. v List of Tables ................................................................................................................... viii List of Figures....................................................................................................................ix Introductory Image .......................................................................................................... xiv Chapter 1. Introduction ............................................................................................... 1 1.1. Magma plumbing systems ........................................................................................ 1 1.1.1. Basaltic volcanoes ...................................................................................... 1 1.1.2. Composition ................................................................................................ 3 1.1.3. Current understanding ................................................................................ 4 1.1.4. Persistent activity ........................................................................................ 7 1.1.5. The importance of constraining magmatic plumbing systems .................... 7 1.2. Masaya volcano, Nicaragua ..................................................................................... 8 1.2.1. Location and tectonic setting ...................................................................... 8 1.2.2. Historical activity ....................................................................................... 10 1.2.3. Plinian eruptions and Masaya’s caldera ................................................... 12 1.2.4. Chemistry .................................................................................................. 12 1.2.5. Density structure ....................................................................................... 13 1.3. Mauna Loa volcano, Hawaii, USA .......................................................................... 14 1.3.1. Location and Hawaiian Volcanism ............................................................ 14 1.3.2. Recent activity and topography ................................................................. 16 1.3.3. Previous studies - The Nīnole Hills ........................................................... 19 1.4. Thesis Structure ..................................................................................................... 20 1.5. References ............................................................................................................. 21 Chapter 2. General Methodology ............................................................................. 28 2.1. Magnetics ............................................................................................................... 28 2.1.1. Background ............................................................................................... 28 2.1.2. Survey procedures .................................................................................... 29 2.2. Gravity .................................................................................................................... 31 2.2.1. Background ............................................................................................... 31 2.2.2. Satellite Gravity Data ................................................................................ 35 2.2.3. Surveying .................................................................................................. 35 2.3. Melt inclusion geochemistry ................................................................................... 36 2.3.1. Background ............................................................................................... 36 2.3.2. Data collection .........................................................................................